Class II treatment with fixed functional orthodontic appliances before and after the pubertal growth peak - a cephalometric study to evaluate differential therapeutic effects

Abstract

Objective: The aim of this clinical trial was to investigate and compare outcomes after treating a skeletal Class II malocclusion with two fixed functional orthodontic appliances, the Herbst appliance and the Functional Mandibular Advancer, by evaluating their skeletal and dentoalveolar effects and the repercussion on the profile in relation to patient age.

Patients and methods: The sample population comprised 42 subjects with skeletal Class II malocclusion. They were divided into two groups depending on age. Group A (n = 21) included nine female subjects aged up to 12 years and twelve male subjects aged up to 14 years. Group B (n = 21) comprised twelve females older than 12 years and nine males older than 14 years. Treatment course was documented cephalometricly. The net therapeutic effects were calculated with reference to the control group.

Results: A significant reduction of the overjet was achieved in both treatment groups. Within the two groups there were no significant sagittal effects in terms of mandibular advancement. However, there was an inhibiting effect on the maxilla, which counteracted the natural growth process. Significant changes in vertical direction were detected mainly in the younger patients in the sense of lengthening of the lower face. Significant dental changes were predominantly found in the group of older patients. For instance, treatment with fixed functional orthodontic appliances led to retrusion of the upper incisors by a mean of 2.21 mm +/- 2.66 mm (p = 0.0015), protrusion of the lower incisors by a mean of 2.28 mm +/- 2.39 mm (p = <or= 0.0001) and distalization of the six-year molars by a mean of 1.12 mm +/- 2.15 mm (p = 0.0315). The skeletal and dental effects achieved by treatment did not correlate directly with the soft tissue adaptations. Generally speaking, far more significant effects on the soft tissue profile were identified in the younger patients. Significant reduction in convexity of the bony profile was similarly more pronounced than in the older age group (N-A-Pog: group A: -4.46 +/- 3.00 (p <or= 0.0001), group B: 3.93 +/- 3.25 (p <or= 0.0001).

Conclusions: Only slight skeletal sagittal effects, which were independent of age, were observed as a result of treatment with fixed functional orthodontic appliances. The younger the patients, the greater any growth-inhibiting effect on the maxilla will be. There is a greater increase in facial height during treatment than would have been expected from growth without any such influence. The compensatory dental effects increase with patient age.